Digital Subscriber Line
Voice does not use all the available bandwidth on a phone line—it uses
frequencies only up to about 3 kHz. DSL was created to use the space between
3 kHz and 1 MHz to send data traffic over a telephone local loop. Thus, both
voice and data can be sent simultaneously over the same connection (some
variants of DSL use the entire spectrum, however, so no voice can be sent).
DSL is a physical layer medium that extends between the subscriber’s DSL
modem and the provider’s DSL access multiplexer (DSLAM.)